CODEWITHSUNDEEP
javarecursion
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Reputation: 357

Recursive Statement not Instantly Returning

I am creating a method that takes a list of numbers and an index.

If there is a number after the index that is six times the first number, it returns true. Otherwise, it returns false.

 public static boolean firstElementMultiple(int []Numbers, int index) {
        System.out.println(Numbers[index]);

        if ((Numbers[0]*6)==Numbers[index]){
            System.out.println("Yep");
            return true;
        }

        if (index+1 >= Numbers.length){
            return false;
        }


        firstElementMultiple(Numbers, index+1);

        return false;

With a list of {5,6,7,30} and an index of 1, false is returned, even though 30 is in the list.

6 7 30 Yep

Is printed, which shows me that it did recognise that 30 was in the list. However, it is still returning false even though the next statement is true and should stop the method?

This has to be done by recursion.

edit: I have to put the 'return false;' at the end as, without it, it doesn't let me. However, I don't see how it can ever get there because there is always a recursive call in the way.

Upvotes: 0

Views: 133

Answers (2)

Abhinav Kaushal Keshari
Abhinav Kaushal Keshari

Reputation: 578

Because in the end, you are returning false in your recursive function no matter what you get in further calculations. You should change your code to this:

public static boolean firstElementMultiple(int []Numbers, int index) {
    System.out.println(Numbers[index]);

    if ((Numbers[0]*6)==Numbers[index]){
        System.out.println("Yep");
        return true;
    }

    if (index+1 >= Numbers.length){
        return false;
    }

    return firstElementMultiple(Numbers, index+1);
}

Basically you need to change

firstElementMultiple(Numbers, index+1);
return false;

to

return firstElementMultiple(Numbers, index+1);

Upvotes: 1

Silvio Mayolo
Silvio Mayolo

Reputation: 70357

firstElementMultiple(Numbers, index+1);
return false;

Here's the end of your method. This is what it does. It says "Call firstElementMultiple to keep looking for the value we're looking for. Once you've finished looking, completely ignore whether or not you found it and return false anyway."

Given that, how can you fix it to do what you want it to do, namely return whether or not we found the element?

Upvotes: 1

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